Reduction of Noise in Fundamental Mode Orthogonal Fluxgates by Optimization of Excitation Current
Reduction of Noise in Fundamental Mode Orthogonal Fluxgates by Optimization of Excitation Current
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DOI：
10.1109/tmag.2011.2152379
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发表时间：
2011-10-01
影响因子：
2.1
通讯作者：
Sasada, Ichiro
中科院分区：
文献类型：
--
作者：
Butta, Mattia;Yamashita, S.;Sasada, Ichiro
降低噪声是正交磁通门的一个主要问题，因为这种传感器的主要缺点是比并行磁通门的噪声更高。由于励磁电流中添加了直流偏置，基模正交磁通门被成功地提出来降低噪声水平。研究表明，基模正交磁通门抑制噪声的主要原因是大直流偏置下获得的巴克豪森噪声的减少，这使得励磁电流单极性并避免磁化强度反转。因此，人们可能认为低交流电流和大直流偏压总是有利的。在本文中，我们将证明，当该传感器用于以反馈模式运行的磁力计时，情况并不总是如此。对于给定的直流偏置，当我们增加交流电流时，由于环路内部灵敏度的增加，1/f 噪声将会下降。 1/f 噪声将达到最低水平，然后如果我们进一步增加交流电流，它将回升，因为巴克豪森噪声的增量超过了灵敏度的增量。最小点也通过圆周磁通电流环的测量来验证。通过正确选择激励电流参数，我们在 1 Hz 时实现了 2.5 pT/root Hz 的本底噪声和 7 pT/root Hz 的噪声。最后提出了一个通用规则来轻松最小化噪声。
Reduction of noise is a major issue for orthogonal fluxgates, since the main drawback of this kind of sensor is higher noise than parallel fluxgates. Fundamental mode orthogonal fluxgates were successfully proposed to reduce the noise level, thanks to dc bias added to the excitation current. It has been shown that the main reason for noise suppression in fundamental mode orthogonal fluxgates is the reduction of Barkhausen noise obtained with a large dc bias, which makes the excitation current unipolar and avoids reversal of magnetization. Thus, one might believe that a low ac current and a large dc bias are always advantageous. In this paper we will show that this is not always true when this sensor is used in a magnetometer operated in feedback mode. For a given dc bias the 1/f noise will drop when we increase the ac current due to the increment of sensitivity inside the loop. The 1/f noise will reach a minimum level, and then if we further increase the ac current it will rise back up because the increment of Barkhausen noise becomes predominant over the increment of sensitivity. The minimum point is also verified by measurement of circumferential flux-current loop. By properly choosing excitation current parameters, we achieved a 2.5 pT/root Hz noise floor and 7 pT/root Hz noise at 1 Hz. A general rule is finally proposed to easily minimize the noise.